1. Field of the Invention
The present invention relates to a compact disc (CD) and digital versatile disc (DVD) system, and more particularly, to an apparatus and method for generating a pulse for recording data on an optical disc in a rewritable CD/DVD (hereinafter referred to as “a CD-RW/DVD-RW”).
2. Description of the Related Art
Optical discs such as a CD-RW/DVD-RW are used in storing a large amount of audio, video and/or data. A process for recording data on an optical disc includes encoding and modulation. Referring to FIG. 1, the process for recording data on an optical disc will now be described. FIG. 1 shows non return to zero (NRZ) data in a CD-RW/DVD-RW system and a pulse signal for actual recording together with a clock signal.
The CD-RW/DVD-RW system uses an eight-to-fourteen modulation (EFM)/EFM+ method as a modulation method. EFM/EFM+ modulated data is non return to zero inversion (NRZI) data. NRZI data formed of ‘1’ and ‘0’ is converted into NRZ data which is inverted whenever an event (a time when transition from ‘1’ to ‘0’ or from ‘0’ to ‘1’ occurs) occurs. NRZ data has a pattern formed with a mark and a space. Data which is actually recorded on the optical disc is a pulse (WRTE_PULSE) generated based on the mark of NRZ data. A write strategy in the CD-RW/DVD-RW system means how the pulse (WRITE_PULSE) for recording data on the disc is generated.
In the prior art low-speed CD-RW/DVD-RW system, the location and size of a write pulse (WRITE_PULSE) are adjusted only with the size of the current mark (CM). That is, with respect to the size of the current mark, a pulse having a different delay (Td, Tf) is generated. Generally, delay information (Td, Tf) with respect to the size of a mark is stored in a table in advance, and a write pulse (WRITE_PULSE) is generated by reading delay information corresponding to the size of the current mark (CM).
Recently, in order to enable high speed CD-RW/DVD-RW disc write, a dynamic write strategy has been used. The dynamic write strategy is a technology capable of generating a write pulse considering not only the size of the current mark (CM) but also the sizes of spaces (PS, FS) adjacent to the current mark (CM) and the sizes of marks (PM, FM) adjacent to the current mark (CM).
In an ordinary write strategy, the sizes of a mark and a space are found in an EFM modulated NRZ pattern which is generated and output, and a needed write pulse is generated by reading delay data needed in a corresponding mark. However, in the dynamic write strategy, adjacent marks and spaces should be considered, and buffering of a pattern is needed.
Therefore, an apparatus for pattern buffering is needed. In order to minimize the needed hardware structure and efficiently improve the performances such as the operation speed, a buffering apparatus having a minimum buffering delay and minimum size and a buffering method therefor are needed.